Fans and blowers are known to be used in ventilation applications. They can consume a large share of all electrical energy used in the industry and service sectors. A majority of life-cycle costs of a fan system can be energy costs.
In a ventilation application, the fan system can be equipped with an air filter, for example, to maintain performance of a heat exchanger. The filter can cause an additional pressure drop in the ventilation system, thus, decreasing the efficiency of the fan system. The efficiency can, for example, be represented by the specific fan power SFP (kW/m3/s) which represents power consumption as a function of the flow rate. For known fine filters, an initial pressure drop can, for example, be approximately 50 to 100 Pa when the final pressure at the time of filter change is 200 to 250 Pa. According to the publication Recommendation Concerning Calculating Life Cycle Cost for Air Filters, Eurovent, September, 2005, a filters can be responsible for a large portion of total pressure drop in ventilation systems.
Condition monitoring of an air filter can be carried out by measuring a pressure difference over the air filter. FIG. 1 illustrates an exemplary ventilation fan 10 with an air filter 11. The condition of the air filter can be monitored by a pressure difference measurement 12. An increasing pressure difference can indicate accumulation of dirt in the air filter 11.
This can determine the filter condition but uses extra instrumentation, thus, increasing cost of the system. A related issue is that the pressure loss of the air filter 12 can be influenced by the flow rate through the filter.
In an exemplary embodiment of a method according to the disclosure, accumulation of dirt on an air filter in a ventilation system including the filter and a fan can be accurately detected under different operating conditions.
An amount of dirt in the filter can be estimated on the basis of the effect the dirt has on the operating point of the fan. The operating point can be estimated on the basis of characteristics curves and power of the fan. The power can be estimated on the basis of a mechanical torque and a rotational speed of the fan.
On the basis of the operating point, a filter pressure loss induced by the dirt can be estimated. A specific fan power representing power consumption in respect of a flow rate through the fan can also be calculated on the basis of the operating point. In an exemplary embodiment of a method according to the disclosure, a power loss induced by the dirt accumulating on the filter can be calculated on the basis of the operating point.
Exemplary embodiments of the disclosure are able to accurately detect accumulation of dirt even if the fan system operates under different operating conditions. The accumulation of dirt can be estimated without cost-increasing pressure sensors.